1. Field of the Invention
This invention relates generally to a spray nozzle for use in precision farming. More particularly, but not by way of limitation, the present invention relates to an attitude controller which accounts for vehicle velocity in the delivery of an agricultural product.
2. Background
Precision farming is a term used to describe the management of intrafield variations in soil and crop conditions. Site specific farming, prescription farming, and variable rate application technology are sometimes used synonymously with precision farming to describe the tailoring of soil and crop management to the conditions at discrete, usually contiguous, locations throughout a field. The size of each location depends on a variety of factors, such as the type of operation performed, the type of equipment used, the resolution of the equipment, as well as a host of other factors. Generally speaking, the smaller the location size, the greater the benefits of precision farming, at least down to approximately one square meter.
Typical precision farming techniques include: varying the planting density of individual plants based on the ability of the soil to support growth of the plants; and the selective application of farming products such as herbicides, insecticides, and, of particular interest, fertilizer.
In contrast, the most common farming practice is to apply a product to an entire field at a constant rate of application. The rate of application is selected to maximize crop yield over the entire field. Unfortunately, it would be the exception rather than the rule that all areas of a field have consistent soil conditions and consistent crop conditions. Accordingly, this practice typically results in over application of product over a portion of the field, which wastes money and may actually reduce crop yield, while also resulting in under application of product over other portions of the field, which may also reduce crop yield.
Perhaps even a greater problem with the conventional method is the potential to damage the environment through the over application of chemicals. Excess chemicals, indiscriminately applied to a field, ultimately find their way into the atmosphere, ponds, streams, rivers, and even the aquifer. These chemicals pose a serious threat to water sources, often killing marine life, causing severe increases in algae growth, leading to eutrophication, and contaminating potable water supplies.
Thus it can be seen that there are at least three advantages to implementing precision farming practices. First, precision farming has the potential to increase crop yields which will result in greater profits for the farmer. Second, precision farming may lower the application rates of seeds, herbicides, pesticides, and fertilizer, reducing a farmer""s expense in producing a crop. Finally, precision farming will protect the environment by reducing the amount of excess chemicals applied to a field, which may ultimately end up in the atmosphere, a pond, stream, river, or other water source.
Agricultural applicators that apply fertilizers, pesticides, and other materials are typically attached to a moving tractor and must account for vehicle velocity, material velocity, and elevation above the target, if the machine is to apply the material at the intended rate only to a specific target. Existing applicators are adjusted manually, by trial and error, or use an estimate of the flight time of the applied material and the vehicle velocity to calculate the time at which the applicator is triggered in order to deposit material on the target. The former method does not permit dynamic adjustment for changes in vehicle velocity, material ejection velocity, or elevation of the nozzle above the target. The latter method is difficult to calculate, may not be fast enough to account for changes in elevation of the nozzle above the target and changes in the material ejection velocity, and does not account for differences in the in-flight velocities of different sized particles. In addition, the measurement of elevation changes is difficult and expensive.
The present invention is important because it enables the agronomist to minimize applicator boom height, material exit velocity, and applicator vehicle velocity as factors affecting the location that the material impacts the target surface. The art is developing mobile optical sensing technologies that enable one to identify specific plant targets, determine the amount of material to be applied, and apply material only to the plant target. Applicator boom height, material exit velocity, and vehicle velocity normally vary during farming operations. Current technologies attempt to hold these variables constant, which greatly reduces the flexibility of operation and needlessly complicates the system. A device that automatically counteracts controllable factors causing off target deposition of materials will greatly improve the efficiency of an optical sensor based variable rate applicator.
The invention disclosed herein adjusts the angle of the device emitting the material (hereinafter referred to as the xe2x80x9cnozzlexe2x80x9d) so that the horizontal exit velocity of the material is equal in magnitude and opposite in direction to the applicator vehicle velocity. By negating the horizontal velocity of the vehicle, the horizontal velocity of the material emitted from the nozzle is zero, absent other external disturbances. Consequently, if the material is ejected over the target from any height above the target, it falls onto the target. While the inventive device can apply liquid, granular or gaseous materials, by way of example and not limitation, the preferred embodiment is described herein with regard to the delivery of liquid materials. However, as will be apparent to those skilled in the art, devices to apply granular or gaseous materials would be similar in design.
The nozzle attitude controller consists of a horizontal manifold or pipe, oriented perpendicular to the direction of travel by the applicator-vehicle. This manifold is suspended from a frame or boom. Liquid material is conveyed through the manifold to a series of nozzles oriented perpendicular to the axis of the manifold and in the same plane. The manifold is supported by bearings and is linked to a linear actuator as shown in FIG. 1. The linear actuator rotates the manifold around its axis. Liquid materials are ejected through the nozzle orifice. Ejection velocity can be calculated by:
Vj=Cv(2xcex94p/xcfx81)1/2xe2x80x83xe2x80x83(1)
Where:
VJ=Liquid jet velocity
Cv=nozzle velocity coefficient
xcex94p=difference in pressure across the orifice
xcfx81=liquid density
The velocity coefficient is a known or measurable property of the nozzle; the liquid density is a known or measurable fluid property. Pressure transducers can be installed to measure the spray system differential pressure. The ejection angle, where the horizontal component of liquid velocity is equal to the vehicle velocity, can be calculated by the following equation:
"THgr"=cosxe2x88x921[Vv/Cv(2xcex94p/xcfx81)1/2]xe2x80x83xe2x80x83(2)
Where:
"THgr"=nozzle angle of inclination
Vv=applicator vehicle velocity
Nozzle angle may be measured to provide position feedback for a control system.
Further objects, features, and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following description of the preferred embodiments.